Mexico's National Astronomical Observatory (Spanish: El Observatorio Astronómico Nacional - OAN) was first established on the balcony of Chapultepec Castle in Mexico City in 1878. After several moves to avoid excessive lighting and pollution, the observatory was established in the national park Sierra San Pedro Mártir in Baja California in 1967 at an altitude of 2800m (9200 ft). The site has been found to have excellent astronomical seeing. The observatory has been operated by the National Autonomous University of Mexico (UNAM) since 1929. It hosts three optical telescopes of 2.1m, 1.5m and 0.84m diameter. The national park itself offers the visitor a rare test within Mexico : forest of high pines and oaks with a fantastic wildlife.